Cellular senescence is a recognised mechanism of tumor suppression; however, its contribution to other pathologies is not well understood. We show that the matricellular protein CCN1/CYR61, which is dynamically expressed at sites of wound repair, can induce fibroblast senescence through its cell adhesion receptors, integrin α6β1 and heparan sulfate proteoglycans. CCN1 induces DNA damage response and p53 activation, and activates the RAC1-NOX1 complex to induce reactive oxygen species (ROS) generation and ROS-dependent activation of the p16INK4a/pRb pathway, leading to senescence and concomitant expression of antifibrotic genes. Senescent fibroblasts accumulate in granulation tissues of healing cutaneous wounds and express antifibrotic genes in wild type mice. These processes are obliterated in knockin mice that express a senescence-defective CCN1 mutant, resulting in exacerbated fibrosis. Topical application of CCN1 protein to wounds reverses these defects. Thus, fibroblast senescence is a CCN1-dependent wound healing response in cutaneous injury, functioning to curb fibrosis during tissue repair.

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The CCN family of matricellular proteins is critical for embryonic development and plays important roles in inflammation, wound healing, and injury repair in the adult. Deregulation of their expression or activities contributes to the pathobiology of myriad diseases, many of which may arise when inflammation or tissue injury becomes chronic, including fibrosis, arthrosclerosis, arthritis, diabetic nephropathy and retinopathy, and cancer. Emerging studies indicate that targeting CCN expression or signaling pathways holds promise in the development of diagnostics and therapeutics for such diseases. This review summarizes the biology of CCN proteins, their roles in various pathologies, and potential as therapeutic targets.

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